Air-conditioning unit

ABSTRACT

An air-conditioning unit, in which at least a lead wire ( 14   g ) of a temperature sensor ( 14 ) is inserted in a cylindrically formed grommet ( 16 ), is disclosed. A cylindrical seal portion ( 16   a ) fitted in a hole portion ( 15 ) of a case ( 11 ) is formed at an end of the grommet ( 16 ). The lead wire ( 14   g ) is fitted relatively displaceably on the inner periphery of the cylindrical seal portion ( 16   a ). A cylindrical fixed portion ( 16   d ) fixed with the lead wire ( 14   g ) is formed at the other end of the grommet ( 16 ). A bellows ( 16   b ) is formed between the cylindrical seal portion ( 16   a ) and the cylindrical fixed portion ( 16   d ).

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a sensor assembly structure for an air-conditioning unit having an evaporator or a similar heat exchanger built therein or, in particular, to a sensor assembly structure used for an air-conditioning system for vehicle use.

2. Description of the Related Art

In recent years, demand has increased for improved quietness in a vehicle compartment, and an air-conditioning system for vehicle use employs a configuration in which a heat exchanger such as an evaporator is supported afloat with respect to the case of the air-conditioning unit, through a buffer member.

FIG. 5 shows an outline of a prior art for supporting a heat exchanger in floated position. This structure includes a buffer member 13 arranged between an evaporator 12 making up a heat exchanger for the cooling operation and the inner wall surface of a case 11 of the air-conditioning unit. The buffer member 13 is made of a flexible material such as foamed resin.

The vibration of the vehicle engine is transmitted to the evaporator 12 through a refrigerant pipe (not shown) coupled to a pipe joint portion 20 of the evaporator 12. This vibration of the evaporator 12 is absorbed by the buffer member 13 to suppress the transmission of the vibration to the case 11. In this way, the propagation of the vibration noise from the case 11 into the passenger compartment is suppressed.

A temperature sensor 14 is assembled on the core 12 a of the evaporator 12. The temperature sensor 14 is for detecting the surface temperature of the fins of the core 12 a of the evaporator 12 and, as shown in FIG. 6, includes a sensor holder 14 a formed of resin. The sensor holder 14 a is formed integrally with an engaging piece 14 b having a plurality of engaging pawls 14 c, and assembled on the core 12 a using the engaging piece 14 b.

A cylindrical sensor element unit 14 d is fixedly held on the sensor holder 14 a. This sensor element unit 14 d includes a sensor element (thermistor element) accommodated in a cylindrical heat transfer case formed of a metal.

Two lead wires 14 g are led from the sensor element of the sensor element unit 14 d and are passed out of the case 11 through a fitting hole 15 of the case 11 thereby to connect the lead wires 14 g to a connector 21 arranged on the outer wall surface of the case 11.

A grommet 22 is fixedly fitted on the lead wires 14 g and assembled in the fitting hole 15 of the case 11. The grommet 22, as shown in FIG. 7, is cylindrically formed of a rubber foamed material, and exhibits the functions of a buffer for absorbing vibrations and of a means for sealing the fitting hole 15.

For this purpose, the outer diameter of the grommet 22 is smaller than the inner diameter of the fitting hole 15, and the outer peripheral surface of the grommet 22 is fitted under pressure on the inner peripheral surface of the fitting hole 15 while forming a gap between the inner peripheral surface of the grommet 22 and the lead wires 14 g. As shown in FIG. 7, the part of the lead wires 14 g located outside the case 11 is fixedly fitted with a heat-shrinkable tube 23, which is fixedly bonded at an outer end of the grommet outside the case. Reference numeral 24 in FIG. 7 designates the fixedly bonded part.

The vibration from the engine, etc. is transmitted to the evaporator 12, which is then displaced relatively to the case 11. Then, the sensor holder 14 a is also displaced integrally with the evaporator 12. In the case where the sensor holder 14 a is displaced in such a direction as to compress the lead wires 14 g, the flexibility and displacement of the lead wires 14 g prevents the displacement of the sensor holder 14 a from being transmitted to the case 11.

In the case where the sensor holder 14 a is displaced in such a direction as to tension the lead wires 14 g, on the other hand, the vibration of the evaporator 12 tends to be transmitted to the case 11 through the lead wires 14 g. In the prior art, the part of the grommet 22 shown in FIG. 7 which is projected out of the case (the portion having the projection size L) exhibits a buffer function and absorbs the tension from the lead wires 14 g thereby to suppress vibration transmission to the case 11.

FIG. 8 shows the relation between the deformation resistance of the grommet 22 and the projection size L of the grommet 22 out of the case 11 with the evaporator 12 (sensor holder 14 a) displaced by a predetermined small amount. With the increase in the projection size L, the deformation resistance of the grommet 22 is decreased as indicated by dashed line X.

A study by the present inventors has revealed that, in the case where the projection size L of the grommet 22 is set to not less than 10 mm, the deformation resistance of the grommet 22 can be reduced to less than a predetermined level Y. As a result, it has been discovered that the vibration transmission to the case 11 through the lead wires 14 g can be suppressed satisfactorily.

In the case where the projection size L of the grommet 22 out of the case 11 is set to not less than 10 mm, the leg of an occupant comes into contact with the lead wires 14 g or the part of the grommet 22 projected out of the case 11 and the lead wires 14 g or the grommet 22, as the case may be, may be damaged.

In view of this, the present inventors have studied a configuration in which, as shown in FIG. 9, an elongate grommet 25 is set between the sensor holder 14 a and the case 11, so that the part of the grommet 25 located within the case 11 absorbs the vibration of the sensor holder 14 a and the projection size L of the grommet 25 out of the case 11 can be reduced. This configuration, however, has the disadvantage that condensed water w is liable to attach to the cylindrical part of the grommet 25 located within the case 11 and, by travelling along the surface of the grommet 25, leak out of the case 11 by way of the fitting hole 15.

SUMMARY OF THE INVENTION

This invention has been achieved in view of the above-mentioned points, and an object thereof is to provide a sensor assembly structure for an air-conditioning unit which can absorb the vibration sufficiently even in the case where the projection size of the grommet, out of the case, is reduced.

Another object of the invention is to provide a sensor assembly structure for an air-conditioning unit which can secure the water leakage prevention effect.

Still another object of the invention is to provide a sensor assembly structure for the air-conditioning unit having a high sensor assembly workability.

In order to accomplish the above object, according to a first aspect of the present invention, there is provided an air-conditioning unit comprising a heat exchanger (12) supported afloat through a buffer member (13) in a case (11) forming an air path, and a sensor (14) for detecting a physical value indicating the condition of the heat exchanger (12),

wherein the sensor (14) includes a sensor element (14 f), at least a lead wire (14 g) electrically connected to the sensor element (14 f) and a sensor holder (14 a) assembled on the heat exchanger (12) for holding the sensor element (14 f),

wherein the case (11) includes a hole portion (15) for leading the lead wire (14 g) out of the case (11),

wherein the lead wire (14 g) is inserted into the cylindrical interior of a grommet (16) cylindrically formed of an elastic material having a high flexibility,

wherein a cylindrical seal portion (16 a) is fitted in the hole portion (15) and pressed against the wall surface of the case (11) at an end of the grommet (16),

wherein the lead wire (14 g) is fitted relatively displaceably on the cylindrical seal portion (16 a) on'the inner periphery of the cylindrical seal portion (16 a),

wherein a fixed portion (16 d) fixed with the lead wire (14 g) is formed at the other end of the grommet (16), and

wherein the portion of the grommet (16) between the cylindrical seal portion (16 a) and the fixed portion (16 d) is formed as a bellows (16 b).

When the heat exchanger (12) is displaced relatively to the case (11) by the vibration applied to the heat exchanger (12), the sensor holder (14 a) and the lead wires (14 g) are displaced integrally with the heat exchanger (12), and therefore the displacement of the lead wires (14 g) is transmitted to a fixed portion (16 d) at the other end of the grommet (16).

In this process, according to the invention, a bellows (16 b) formed between the fixed portion (16 d) and the cylindrical seal portion (16 a) expands/shrinks and can sufficiently absorb the vibratory displacement of the lead wires (14 g). As a result, the vibratory displacement of the lead wires (14 g) can be sufficiently prevented from being transmitted to the case (11) through the grommet (16).

According to a second aspect of the present invention, the case (11) is configured by integrally fastening a plurality of division cases (11 a, 11 b), and

wherein the hole portion (15) is formed in the fitting coupling surface of the plurality of the division cases (11 a, 11 b).

According to a third aspect of the present invention, the sensor holder (14 a) includes a projection (14 i) extending to the fixed portion (16 d), and wherein the fixed portion (16 d) and the lead wire (14 g) are fixed on the projection (14 i).

The projection (14 i) can be configured as a rigid member integrally with the sensor holder (14 a). In the state where the grommet (16) is assembled on the sensor (14), the projection (14 i) naturally sets the grommet (16) in position with respect to the sensor holder (14 a). As a result, the grommet (16) can be easily assembled automatically in the fitting hole (15) of the case (11).

According to a fourth aspect of the present invention, the fixed portion (16 d) is cylindrical and the projection (14 i) is inserted into the cylinder of the fixed portion (16 d).

By doing so, the fixed portion (16 d) is easily, positively fixed on the projection (14 i) together with the lead wires (14 g).

According to a fifth aspect of the present invention, the outer diameter of the cylinder of the fixed portion (16 d) is smaller than the outer diameter of the cylindrical seal portion (16 a).

According to a sixth aspect of the present invention, a bell-shaped enlarged portion (16 e) having a progressively increasing diameter is formed at the end of the cylindrical fixed portion (16 e) nearer to the sensor holder (14 a).

According to a seventh aspect of the present invention, the heat exchanger (12) is a cooling heat exchanger for cooling and dehumidifying the air, wherein the sensor (14) is arranged downstream of the cooling heat exchanger (12) in the air flow, so that the condensed water generated by the cooling heat exchanger (12) is attached to the fixed portion (16 d), and wherein the portion of the grommet (16) nearer to the cylindrical seal portion (16 a) than the fixed portion (16 d) is formed with a weather board (16 c) for catching and drops the condensed water due to its own weight.

Consequently, the condensed water attached to the fixed portion (16 d) is prevented from being transferred to the cylindrical seal portion (16 a), which in turn prevents water leakage from the hole (15) of the case (11).

According to an eighth aspect of the present invention, the bellows (16 b) is formed as a circle when viewed in axial direction of the cylindrical grommet (16).

According to a ninth aspect of the present invention, the bellows (16 b) is formed as a polygon when viewed in axial direction of the cylindrical grommet (16).

According to a tenth aspect of the present invention, the cross section of the bellows (16 b) along the axial direction of the grommet (16) is smoothly-expanded in a curved form radially outward of the grommet (16).

According to an eleventh aspect of the present invention, the cross section of the bellows (16 b) along the axial direction of the cylindrical grommet (16) is linearly expanded as a flat surface radially outward of the grommet (16).

According to a twelfth aspect of the present invention, the cross section of the bellows (16 b) along the axial direction of the cylindrical grommet (16) is reduced to a narrowed root at the expansion making up the bellows (16 b).

According to a thirteenth aspect of the present invention, the cross section of the bellows (16 b) along the axial direction of the cylindrical grommet (16) is so configured that one side of the expansion making up the bellows (16 b) in the axial direction of the grommet (16) is a flat surface, and the other side of the expansion is a Z-shaped bend.

According to a fourteenth aspect of the present invention, the cross section of the bellows (16 b) along the axial direction of the cylindrical grommet (16) includes an expansion making up the bellows (16 b) having a Z-shaped bend on both axial sides thereof.

According to an fifteenth aspect of the present invention, a plurality of the bellows (16 b) are formed successively in the axial direction of the cylindrical grommet (16).

According to a sixteenth aspect of the present invention, the plurality of the bellows (16 b) each have an independent annular form.

According to a seventeenth aspect of the present invention, the plurality of the bellows (16 b) have a continuous spiral form.

Incidentally, the reference numerals in parentheses, to denote the above means, are intended to show the relationship of the specific means which will be described later in an embodiment of the invention.

The present invention may be more fully understood from the description of preferred embodiments of the invention set forth below, together with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing the essential parts of the air-conditioning unit according to an embodiment of the invention.

FIG. 2A is a sectional view taken in line A-A in FIG. 1, and FIG. 2B a front view of the grommet bellows in FIG. 2A.

FIG. 3 is a sectional view taken in line B-B in FIG. 1.

FIG. 4 is a sectional view taken in line C-C in FIG. 2A.

FIG. 5 is a sectional view schematically showing the essential parts of the sensor assembly structure for the conventional air-conditioning unit.

FIG. 6 is a diagram showing a general layout of a temperature sensor, a vibration-proof grommet and a connector according to the prior art.

FIG. 7 is an enlarged sectional view showing the essential parts of the vibration-proof grommet assembly structure according the prior art.

FIG. 8 is a graph showing the relation between the projection size of the vibration-proof grommet and the deformation resistance.

FIG. 9 is a general sectional view showing the essential parts of the sensor assembly structure for the air-conditioning unit studied by the inventor.

FIGS. 10A to 10K are diagrams for explaining modifications of the bellows of the vibration-proof grommet according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the invention is described with reference to the drawings. FIG. 1 is a sectional view showing the essential parts of the air-conditioning unit 10 using the sensor assembly structure according to the invention. FIG. 2A is a sectional view taken in line A-A in FIG. 1. FIG. 2B is a front view of the grommet bellows shown in FIG. 2A. FIG. 3 is a sectional view taken in line C-C in FIG. 2A. The vertical, horizontal and longitudinal directions in FIGS. 1, 2A are those of the vehicle.

The case 11 of the air-conditioning unit 10 has the two functions of forming an air path of the air-conditioning air on the one hand and accommodating the devices including a heat exchanger such as the evaporator 12 and a door (not shown) for opening/closing the air path on the other hand. The case 11 is formed of resin and divided into a plurality of division cases 11 a, 11 b for the convenience of releasing the resin-molding dies and assembling the accommodated devices. The fit coupling surfaces of the plurality of the division cases 11 a, 11 b are integrally fastened thereby to construct the case 11.

According to this embodiment, as shown in FIG. 2A, the case 11 is configured of the two cases 11 a, 11 b divided along the vehicle length, i.e. a vehicle front case 11 a and a vehicle rear case 11 b. An evaporator 12 is arranged in the case 11 (division cases 11 a, 11 b). According to this embodiment, the evaporator 12 is arranged in such a manner that the longitudinal direction of the tube 12 b of the core 12 a is directed vertically.

The tube 12 b is a flat tube having a flat cross section as shown in FIG. 3. The fin 12 c, on the other hand, is a corrugated fin bent and formed as shown in FIG. 1. The fin 12 c is formed with a plurality of well-known louvers 12 d (FIG. 3) cut obliquely.

The tube 12 b and the fin 12 c are formed of a metal such as aluminum, and a multiplicity of the tubes 12 b and the fins 12 c are alternately stacked in the horizontal direction in FIG. 1 (the horizontal direction of the vehicle). The tubes 12 b and the fins 12 c are coupled integrally with each other by brazing.

The air-conditioning air (internal or external air) is blown by a blower not shown from the vehicle front rearward as indicated by arrow a in FIG. 2A in the case 11 (division cases 11 a, 11 b), and passed through the gap between the fins 12 c and the tubes 12 b of the core 12 a of the evaporator 12.

The longitudinal ends (in the vertical direction of the vehicle) of the tubes 12 b are coupled to a tank 12 e, and the internal refrigerant path of the tubes 12 b communicates with the refrigerant path in the tank 12 e. Although FIG. 1 shows only the configuration for coupling the lower end of the tubes 12 b to the lower tank 12 e, the upper end (not shown) of the tubes 12 b is also coupled to an upper tank portion (not shown).

A side plate 12 f is arranged at an end of the tubes 12 b and the fins 12 c along the stacking direction (horizontal direction). The outermost fin 12 c is coupled to the side plate 12 f, and the longitudinal ends of the side plate 12 f are coupled to a lower tank portion 12 e and an upper tank portion (not shown).

The side plate 12 f has a cross section shown in FIG. 3, which is bent with a protrusion 12 g formed at the central portion along the width (longitudinally of the vehicle). The central protrusion 12 g is the highest projection from the bottom of the side plate 12 f. Although only the side plate 12 f at the left end of the core 12 is shown FIG. 1, a side plate (not shown) having the same configuration is arranged also at the right end of the core 12 a.

A vibration-proof buffer member 13 is wound and fixedly bonded over the whole periphery of the central protrusion 12 g of the left and right side plates 12 f and the central portion along the width (longitudinal direction of the vehicle) of the upper and lower tanks 12 e of the evaporator 12. As a result, by assembling the evaporator 12 in the case 11 and fastening the two division cases 11 a, 11 b integrally by fastening means such as a screw or a metal spring clip, the buffer member 13 is interposed between the outer surface of the evaporator 12 and the inner wall surface of the case 11.

In this way, the evaporator 12 is supported afloat on the inner wall surface of the case 11 by the buffer member 13, and accommodated relatively displaceably with respect to the case 11. This buffer member 13 is formed of an elastic material, high in flexibility, such as foamed resin.

Next, the temperature sensor 14 for detecting the temperature of the evaporator 12 is explained. According to this embodiment, the temperature sensor 14 is arranged on the surface of the core 12 a of the evaporator 12 downstream in the air flow to detect the fin surface temperature of the core 12 a of the evaporator 12 directly. The fin surface temperature thus detected is used for various air-conditioning control operations including the outlet air temperature control and the compressor capability control for the air-conditioning control system for vehicle use.

The temperature sensor 14 specifically includes a sensor holder 14 a formed of resin. The sensor holder 14 a is a substantially rectangular frame member. A tabular engaging piece 14 b extending as an elongate member in the direction perpendicular to the rectangular contour of the sensor holder 14 a (direction longitudinal of the vehicle) is formed integrally with the sensor holder 14 a, and a plurality of engaging pawls 14 c are formed integrally on both the obverse and reverse surfaces of the engaging piece 14 b.

The width b of the engaging piece 14 b is smaller than the interval between the adjacent tubes 12 b of the core 12 a of the evaporator 12, so that the engaging piece 14 b can be inserted between the tubes 12 b. The plurality of the engaging pawls 14 c of the engaging piece 14 b are engaged with the louvers 12 d of the fins 12, thereby making it possible to fix the sensor holder 14 a on the core 12 a.

The elongate sensor element unit 14 d extending in parallel to the engaging piece 14 b is fixedly held on the sensor holder 14 a. The sensor element unit 14 d accommodates a sensor element (thermistor element) 14 f in the cylindrical heat transfer case 14 e with the forward end thereof closed by a metal such as aluminum.

With the sensor holder 14 a fixed on the core 12 a, the sensor element portion 14 d is inserted between the tubes 12 b of the core 12 a, so that the outer surface of the metal heat transfer case 14 e of the sensor element unit 14 d is in contact with the surface of the fins 12 c, and the surface temperature of the fins 12 c can be detected by the sensor element 14 f.

The two lead wires 14 g electrically connected to the sensor element 14 f of the sensor element unit 14 d are led out from the end of the metal heat transfer case 14 e and, being guided by a depression 14 h (FIG. 1) formed on the sensor holder 14 a, are led toward the fitting hole 15 of the case 11.

The lead wires 14 g are led out of the case 11 through the interior of the cylindrical grommet 16 and are electrically connected to a connector (not shown, corresponding to the connector 21 shown in FIGS. 5, 6) arranged outside the case 11.

The grommet 16 exhibits the function of a buffer to absorb vibration while sealing the fitting hole 15. Preferably, therefore, the grommet 16 is formed of an elastic material having a high flexibility (i.e. low hardness). Also, the grommet 16, which is arranged downstream of the evaporator core 12 a in the air flow and used in an environment in which the condensed water is attached, is preferably waterproof. A preferred specific example of the material satisfying these requirements is ethylene-propylene-diene copolymer (EPDM).

The grommet 16 has a cylindrical seal portion 16 a fitted and held in the fitting hole 15 of the case 11. The fitting hole 15 is formed on the fitting coupling surface of the two division cases 11 a, 11 b. Specifically, therefore, the semicircular depressions formed on the division cases 11 a, 11 b are combined into a single circular fitting hole 15.

The outer diameter D1 of the cylindrical seal portion 16 a of the grommet 16 in free state is a predetermined amount larger than the inner diameter of the fitting hole 15. If, for example, the outer diameter D1 of the cylindrical seal portion 16 a of the grommet 16 is 10 mm and the inner diameter of the fitting hole 15 is 8 mm, when the cylindrical seal portion 16 a of the grommet 16 fitted in the fitting hole 15, the cylindrical seal portion 16 a is compressed and deformed as shown in FIG. 1 into contact with the inner peripheral surface of the fitting hole 15, and therefore the inner peripheral surface of the fitting hole 15 can be sealed.

The inner diameter of the cylindrical seal portion 16 a is set, on the other hand, in such a manner that the lead wires 14 g can be freely displaced relatively to the cylindrical seal portion 16 a while maintaining a predetermined gap between the inner peripheral surface of the cylindrical seal portion 16 a and the lead wires 14 g.

A bellows 16 b is formed adjacent to the end, in the case 11, of the cylindrical seal portion 16 a of the grommet 16. The bellows 16 b, which functions as a buffer to absorb the vibrations, has a radial thickness sufficiently smaller than the radial thickness of the cylindrical seal portion 16 a and expands smoothly in a curved form radially outward from the inner peripheral surface of the cylindrical seal portion 16 a. The contour of the bellows 16 b is circular as shown in FIG. 1(b) according to this embodiment. The outer diameter of the bellows 16 b is equal to the outer diameter D1 of the cylindrical seal portion 16 a.

A weather board 16 c and a cylindrical fixed portion 16 d are formed sequentially inward of the bellows in the case 11. The cylindrical fixed portion 16 d forms a small-diameter cylindrical portion having an outer diameter D2 smaller than the outer diameter D1 of the cylindrical seal portion 16 a. Also, the cylindrical fixed portion 16 d is an elongate cylinder having a larger axial length than the outer diameter D2.

The radial thickness of the cylindrical fixed portion 16 d is as small as that of the bellows 16 d, and the inner diameter of the cylindrical fixed portion 16 d is equal to the inner diameter of the cylindrical seal portion 16 a, the smallest inner diameter of the bellows 16 b and the inner diameter of the weather board 16 c.

The weather board 16 c is an annular plate projected radially outward perpendicularly from the outer peripheral surface of an axial end (the end near to the bellows 16 b) of the cylindrical fixed portion 16 d. The outer diameter of the weather board 16 c is equal to the outer diameter of the bellows 16 b and the outer diameter of the cylindrical seal portion 16 a.

A bell-shaped enlarged portion 16 e having a progressively increased diameter is formed at the other axial end (the end nearer to the sensor holder 14 a) of the cylindrical fixed portion 16 d. The grommet 16 can be easily fitted on the lead wires 14 g of the temperature sensor 14 from the enlarged end of the bell-shaped enlarged portion 16 e.

The side surface of the sensor holder 14 a of resin nearer to the case 11 is formed integrally with a projected stay 14 i inserted in a part of the bell-shaped enlarged portion 16 e and the cylindrical fixed portion 16 d of the grommet 16.

The projected stay 14 i is a rod-shaped member having a semicircular cross section as shown in FIG. 4. Two lead wires 14 g are arranged in juxtaposition on the flat surface of the projected stay 14 i. A heat-shrinkable tube 14 j is fitted on the outside of the lead wires 14 g and the projected stay 14 i.

By heating, and reducing the diameter of, the heat-shrinkable tube 14 j, the lead wires 14 g can be fixed on the projected stay 14 i. The outer diameter the heat-shrinkable tube 14 j after shrinkage is larger than the inner diameter of the cylindrical fixed portion 16 d, and therefore the cylindrical fixed portion 16 d can be fixed under pressure in the heat-shrinkable tube 14 j. As a result, the cylindrical fixed portion 16 d of the grommet 16 is fixed on the projected stay 14 i together with the lead wires 14 g. The grommet 16 is fixed on the projected stay 14 i while the enlarged end of the bell-shaped enlarged portion 16 e is kept in contact with the side surface of the sensor holder 14 a.

Next, the operation and effects of this embodiment are explained. In view of the fact that the evaporator 12 is supported afloat on the case 11 by the buffer member 13, the transmission of the vibration of the vehicle engine, etc. to the evaporator 12 through the refrigerant pipe displaces the evaporator 12 relative to the case 11. In the process, the sensor holder 14 a of resin assembled on the core 12 a of the evaporator 12 is a substantially rigid material and therefore displaced (vibrated) integrally with the evaporator 12.

The cylindrical fixed portion 16 d of the grommet 16 and the lead wires 14 g, which are fixed on the projected stay 14 i of the sensor holder 14 a, are also displaced (vibrated) integrally with the sensor holder 14 a.

In view of the fact that the bellows 16 b, which is easy to deform (expand/shrink) in axial direction of the grommet 16, is formed between the cylindrical fixed portion 16 d and the cylindrical seal portion 16 a of the grommet 16, however, the displacement (vibration) of the cylindrical fixed portion 16 d and the lead wires 14 g is absorbed by the expansion/shrinkage of the bellows 16 b.

Also, as the lead wires 14 g are fitted relatively displaceably (fitted loosely) through a predetermined gap on the inner peripheral surface of the cylindrical seal portion 16 a of the grommet 16, the displacement (vibration) of the sensor holder 14 a is not transmitted to the case 11 through the lead wires 14 g and the cylindrical seal portion 16 a.

Further, the bellows 16 b is formed on the portion of the grommet 16 located inside the case 11, and therefore the projection size L of the grommet 16 out of the case 11 contributes nothing to the vibration absorption.

As a result, the projection size L of the grommet 16 is not required to be as long as not less than 10 mm unlike in the prior art and may be set to a minimum value of not more than 5.5 mm, for example. The projection size L of even substantially zero poses no problem. The risk of the grommet 16 or the lead wires 14 g being damaged is remarkably reduced, which otherwise might be caused by the leg of an occupant coming into contact with the portion of the grommet 16 projected out of the case 11.

Also, according to this embodiment, the bell-shaped enlarged portion 16 e progressively increased in diameter is formed at an axial end (the end nearer to the sensor holder 14 a) of the cylindrical fixed portion 16 d. In assembling the grommet 16 on the temperature sensor 14, therefore, the grommet 16 can be easily fitted on the lead wires 14 g of the temperature sensor 14 from the enlarged end of the bell-shaped enlarged portion 16 e. This improves the workability of assembling the grommet 16 on the temperature sensor 14.

According to this embodiment, the cylindrical fixed portion 16 d is fixed on the projected stay 14 i of the sensor holder 14 a with the enlarged end of the bell-shaped enlarged portion 16 e kept in contact with the side surface of the sensor holder 14 a. With the grommet 16 assembled on the temperature sensor 14, therefore, the cylindrical seal portion 16 a of the grommet 16 can be naturally set in position at a predetermined distance from the sensor holder 14 a.

By assembling the sensor holder 14 a of the temperature sensor 14 on the core 12 a of the evaporator 12 and then assembling the evaporator 12 on one of the division cases 11 a, 11 b, or on the vehicle front case 11 a, for example, the cylindrical seal portion 16 a of the grommet 16 can be naturally set in position in the semicircular depression forming the fitting hole 15 of the vehicle front case 11 a. As a result, the temperature sensor 14 and the grommet 15 can be assembled easily by an automatic assembler using a robot.

As an alternative, the evaporator 12 may be first assembled on the vehicle front case 11 a, after which the sensor holder 14 a of the temperature sensor 14 is assembled on the core 12 a of the evaporator 12 so that the cylindrical seal portion 16 a of the grommet 16 is arranged in the semicircular depression forming the fitting hole 15 of the vehicle front case 11 a.

Also, the cylindrical fixed portion 16 d makes up a portion for fixing the lead wires 14 g and the projected stay 14 i of the sensor holder 14 a, and has the outer diameter D2 smaller than the outer diameter D1 of the cylindrical seal portion 16 a. Therefore, a gap is formed between the small-diameter cylindrical portion of the cylindrical fixed portion 16 d and the surface of the core, 12 a of the evaporator 12, thereby making it possible to avoid direct contact between the cylindrical fixed portion 16 d and the surface of the core 12 a.

As a result, the inconvenience of promoted corrosion on the metal surface is suppressed, which otherwise might be caused by the additive in the component material (rubber-group elastic material) of the grommet 16 attached on the metal (aluminum) surface of the core 12 a.

Also, in view of the fact that the annular weather-board 16 c is projected radially outward perpendicularly from the end of the cylindrical fixed portion 16 d of the grommet 16 nearer to the bellows 16 b, the condensed water attached to the cylindrical fixed portion 16 d or the bell-shaped enlarged portion 16 e and reaching the weather board 16 c is caught by the vertical plate surface of the weather board 16 c. This condensed water thus pooled drops due to its own weight. The condensed water attached to the cylindrical fixed portion 16 d never reaches the fitting hole 15 over the weather-board 16 c and therefore the risk of water leakage from the fitting hole 15 is reduced.

Still another advantage of the invention is that the outer diameter D2 of the cylindrical fixed portion 16 d is smaller than the outer diameter d1 of the cylindrical seal portion 16 a, and therefore the condensed water attached to the cylindrical fixed portion 16 d can be reduced in amount.

Finally, other embodiments will be explained. This invention is not limited to the embodiment described above, and can be variously modified as described below.

(1) In the embodiment described above, the bellows 16 b of the grommet 16 is circular in shape. Nevertheless, the bellows 16 b of the grommet 16 may alternatively be a polygon such as a rectangle as shown in FIG. 10B, a pentagon as shown in FIG. 10C, or a hexagon as shown in FIG. 10D to exhibit a buffer function and to absorb vibration with equal effect. FIG. 10A shows a cross section of the polygonal bellows 16 b shown in FIGS. 10B to 10D.

(2) Although the bellows 16 b of the grommet 16 has a curved cross section smoothly expanding radially outward as shown in FIG. 10A according to the embodiment described above, the cross section of the bellows 16 b may alternatively be expanded linearly as a flat surface radially outward of the grommet 16 as shown in FIG. 10E.

Also, the cross section of the bellows 16 b may be so shaped that the root of the expansion is reduced in size as shown in FIG. 10F.

The cross section of the bellows 16 b may be formed as shown in FIG. 10G in such a manner that one axial side of the expansion is a flat surface and the other axial side thereof a Z-shaped bend. The cross section of the bellows 16 b may alternatively be so formed that, as shown in FIG. 10H, a Z-shaped bend is formed on both axial sides of the expansion.

(3) According to the embodiment described above, only one bellows 16 b of the grommet 16 is formed. As shown in FIG. 10I or 10J, however, a succession of two or three bellows 16 b, respectively, may be arranged in axial direction. In other words, a plurality of bellows 16 b of the grommet 16 may be formed in succession into a multiple bellows structure.

(4) In the examples shown in FIGS. 10I, 10J, a plurality of the bellows 16 b are each formed as an independent circle (ring). Instead, a plurality of bellows 16 may be successively formed spirally as shown in FIG. 10K.

(5) According to the embodiment described above, the temperature sensor 14 is arranged downstream of the evaporator 12 in the air flow, and therefore the condensed water attaches to the grommet 16. For this reason, the weather board 16 c is formed on the grommet 16. In the case where the temperature sensor 14 is arranged upstream of the evaporator 12 in the air flow, however, no condensed water attaches to the grommet 16 and therefore the weather-board 16 c is not needed.

(6) According to the embodiment described above, the outer diameter D2 of the cylindrical fixed portion 16 d is smaller by a predetermined amount than the outer diameter D1 of the cylindrical seal portion 16 a of the grommet 16, so that the cylindrical fixed portion 16 d is kept out of direct contact with the surface of the core 12 a. As long as the material of the grommet 16 has no effect on corrosion on the metal surface of the core 12 a, however, the outer diameter D2 of the cylindrical fixed portion 16 d may be equal to the outer diameter D1 of the cylindrical seal portion 16 a.

(7) According to the embodiment described above, the metal heat-transfer case 14 e of the sensor element unit 14 d of the temperature sensor 14 is brought into contact with the surface of the fins 12 c of the core 12 a thereby to detect the surface temperature of the fins 12 c. As an alternative, the sensor element unit 14 d of the temperature sensor 14 may be arranged at the portion of the core 12 a immediately after the air outlet to detect the air temperature (cold air temperature) immediately after the air outlet.

(8) This invention may be applied to an air-conditioning control unit having a pressure sensor for detecting the refrigerant pressure of the evaporator 12, or an air-conditioning control unit having a temperature sensor included in the heat exchanger for the heating operation such as a hot water radiator instead of the heat exchanger for the cooling operation such as the evaporator 12.

While the invention has been described by reference to specific embodiments chosen for purposes of illustration, it should be apparent that numerous modifications could be made thereto, by those skilled in the art, without departing from the basic concept and scope of the invention. 

1. An air-conditioning unit comprising a heat exchanger supported afloat through a buffer member in a case forming an air path, and a sensor for detecting a physical value indicating the condition of the heat exchanger, wherein the sensor includes a sensor element, at least a lead wire electrically connected to the sensor element and a sensor holder assembled on the heat exchanger for holding the sensor element, wherein the case includes a hole portion for leading the lead wire out of the case, wherein the lead wire is inserted into the cylindrical interior of a grommet cylindrically formed of an elastic material having a high flexibility, wherein a cylindrical seal portion is fitted in the hole portion and pressed against the wall surface of the case at an end of the grommet, wherein the lead wire is fitted relatively displaceably on the cylindrical seal portion on the inner periphery of the cylindrical seal portion, wherein a fixed portion fixed with the lead wire is formed at the other end of the grommet, and wherein the portion of the grommet between the cylindrical seal portion and the fixed portion is formed as a bellows.
 2. An air-conditioning unit according to claim 1, wherein the case is configured by integrally fastening a plurality of division cases, and wherein the hole portion is formed in the fitting coupling surface of the plurality of the division cases.
 3. An air-conditioning unit according to claim 1, wherein the sensor holder includes a projection extending to the fixed portion, and wherein the fixed portion and the lead wire are fixed on the projection.
 4. An air-conditioning unit according to claim 3, wherein the fixed portion is cylindrical and the projection is inserted into the cylinder of the fixed portion.
 5. An air-conditioning unit according to claim 4, wherein the outer diameter of the cylinder of the fixed portion is smaller than the outer diameter of the cylindrical seal portion.
 6. An air-conditioning unit according to claim 4, wherein a bell-shaped enlarged portion having a progressively increasing diameter is formed at the end of the cylindrical fixed portion nearer to the sensor holder.
 7. An air-conditioning unit according to claim 1, wherein the heat exchanger is a cooling heat exchanger for cooling and dehumidifying the air, wherein the sensor is arranged downstream of the cooling heat exchanger in the air flow, so that the condensed water generated by the cooling heat exchanger is attached to the fixed portion, and wherein the portion of the grommet nearer to the cylindrical seal portion than the fixed portion is formed with a weather-board for catching and removing the condensed water drops due to its own weight.
 8. An air-conditioning unit according to claim 1, wherein the bellows is formed as a circle when viewed in axial direction of the cylindrical grommet.
 9. An air-conditioning unit according to claim 1, wherein the bellows is formed as a polygon when viewed in axial direction of the cylindrical grommet.
 10. An air-conditioning unit according to claim 1, wherein the cross section of the bellows along the axial direction of the grommet is smoothly expanded in a curved form radially outward of the grommet.
 11. An air-conditioning unit according to claim 1, wherein the cross section of the bellows along the axial direction of the cylindrical grommet is linearly expanded as a flat surface radially outward of the grommet.
 12. An air-conditioning unit according to claim 1, wherein the cross section of the bellows along the axial direction of the cylindrical grommet is reduced to a narrowed root at the expansion making up the bellows.
 13. An air-conditioning unit according to claim 1, wherein the cross section of the bellows along the axial direction of the cylindrical grommet is so configured that one side of the expansion making up the bellows in the axial direction of the grommet is a flat surface, and the other side of the expansion is a Z-shaped bend.
 14. An air-conditioning unit according to claim 1, wherein the cross section of the bellows along the axial direction of the cylindrical grommet includes an expansion making up the bellows having a Z-shaped bend on both axial sides thereof.
 15. An air-conditioning unit according to claim 1, wherein a plurality of the bellows are formed successively in the axial direction of the cylindrical grommet.
 16. An air-conditioning unit according to claim 15, wherein the plurality of the bellows each have an independent annular form.
 17. An air-conditioning unit according to claim 15, wherein the plurality of the bellows have a continuous spiral form. 